This may well sort the problem out but if you still have issues, wait for the Forum Team to get to the thread and they will be able to contact you for account access and address any other problems you have.

I have exactly the same problem, and am relieved to see that someone else is also experiencing it. I've tried all the standard fixes, and a few others that I learned along the way, and I'm entirely sure that it is unrelated to device, browser, cookies, or anything else that could make it "my fault". I saw a warning last week that there would be maintenance on My Vodafone at the end of the week, so I waited to see if that made any difference - but it didn't.

When I was a CC, I had a small tribe of PAYG SIMs, to conduct "compare and contrast" experiments. I imagine that most of them will have been cancelled off by now through lack of use, but a number of those accounts (including my main account) have account numbers beginning AM, whereas the later ones are entirely numeric. I'll work through my list, and see how many of the accounts are still active, and whether it's just the alphanumeric ones that are affected by the problem.

I'm extremely busy just now, so it may take me a day or two, but I'll report as soon as I have gathered some data!

I’ve now had a chance to check things out – the main delay was locating my stock of spare SIMs! I’ve looked at a total of ten PAYG accounts.

Three numbers have presumably lapsed through non-usage and the SIMs no longer function; the account numbers were entirely numeric when they existed and login was what I’d have expected under the circumstances – having given my username and password, I was offered only the alternative contact number(s) to receive the 2LA code, and when I had logged in I was informed that there was no phone number associated with the account, but all my personal and contact details were present and correct. I’m not sure how long these details stay around – a year or two, I’d guess; a few months back I noticed a bizarre thread from someone who imagined that the whole lot would disappear immediately on request!

Four (all with entirely numeric account numbers) functioned correctly, offering me a choice of the main account number and the alternative contact number(s) to receive the 2LA code, and showing me the normal amount of account info once I had logged in.

Three (all older accounts with alphanumeric account numbers beginning AM) produced the error described above. Interestingly, as well as the error against Account Summary, there were options for Billing (which unsurprisingly for PAYG left me up a gum tree), and Account Settings. Choosing the latter, I was offered my alternative numbers to receive the 2LA code. Once I had logged in I was able to see all my personal and contact details, but there continued to be an error report when I tried to view Account Summary.

It seems clear that a programming error has occurred, resulting in the system being unable to cope with the older alphanumeric account numbers. I presume that someone was blithely unaware that earlier accounts had IDs in this format, but the error needs to be rectified soon as it’s difficult to manage long-term without access to the online account.

Vodafone's forum team monitor all the posts here, so I imagine that one of them will pick up the issue and pass it on to be rectified. I don't think anyone can have seen it yet, as my images haven't been approved.

Disregarding my "empty" accounts, you and I between us muster 5 numeric accounts which behave correctly and 5 alphanumeric accounts which encounter the Invalid Data Value - AccountID should be Numeric error. I'd hope that would be sufficient evidence of the specific problem - though I have to admit that one reason for my ridiculous number of "experimental" SIMs was the remarkably high threshold of proof required that any problem, even when widely reported, wasn't just an account-specific issue.

I too have this problem. My account also begins with AM. I contacted teh suport centre yesterday, but they didn't seem to grasp the problem even though I sent them a copy of the error message. Just reset my password! This is what I get on my account summary page

@mike37p@juds Thanks for flagging this with us (and thanks @Annie_N for your tests and looking into this further for us!). So that we can help with the error messages that you're currently seeing when signing in to your online account, please follow the details I've provided in the private message that I've sent to you both. A member of our team will then be in touch.

I'm getting the same error here. I'm actually much more annoyed at the amount of frustration I've spent trying to report the error to Vodafone. They've reset my password and username several times, asked me to send the error in about 3 times and reset cookies etc etc again. They even gave me a escalation number saying I would be contacted which of course I have not. and they asked for all the same information again. So in summary more hassle than it's worth really I will probably just keep it to use with teh one tariff, all the other PAYG providers let you use your balance to buy bundles these days which was what I was looking to do. I think I could still do this but I've already switched to Tesco who have a much better standard bundle deal any way.

I should have checked this forum first I was thininking it might be related to my broadband login

@Natasha I was planning to follow the instructions in your PM, but, on reflection, attempting to deal with the situation by fixing one account at a time - presumably by giving us new accounts - is going to be hideously heavy on manpower. My husband had to have his account replaced a while ago, and it isn't the world's easiest process - we fouled up at the first attempt, and had to go through it twice.

I'm not sure how long ago the format of account numbers changed (within the past 10 years, from the evidence of my records) but there must be thousands of us affected by this, possibly tens of thousands or more, all long-standing customers with quite a track-record of loyalty. Some probably won't discover for some months that they can no longer access their accounts, especially relatively low-rate users with non-smart phones, but this doesn't mean that alienating them is consequence-free.

For some of those affected, the app is unlikely to be an alternative at all, and frankly the app is still pretty rubbishy for PAYG; and the group will include plenty of customers like me who have had their accounts for 20 years or more, and are still quite proud to say "I'm with Vodafone". If CS or Live Chat repeatedly puts customers through what are clearly inappropriate hoops, this is just going to alienate customers further, and plenty of them are going to follow srpsrp's example, and take their business elsewhere. Around here signal is poor, and Vodafone is marginally better than the other networks, so sentiment plus inertia will probably keep me here, but the increasing profile, availabiity and quality of the rivals serves as a permanent reminder that one of the glories of PAYG is the freedom to leave whenever one feels like it.

Since the problem seems to have taken Vodafone by surprise, I assume the change in programming was inadvertent and can be reversed. If there is some good reason why it can't be reversed, then either the old account numbers need to be replaced in some automated way or there needs to be some attempt to alert customers, and CS and Live Chat need to be made aware of what advice to give customers, rather than endlessly and pointlessly resetting passwords.

For the moment, I think I'll just keep the situation under review.

[I've assumed that PayM accounts aren't affected - if they are, things could get very "interesting".]

I agree with this. This (to my mind - I've been in the sofware applications support area for 40 years) is a programming issue and must be a simple validation statement that has been included recently. However there might be other places with the same assumption. I'm amazed this got through any testing - certainly no regression tests seem to have been done.

If it comes to changing my account I'll look to other suppliers and leave Vodafone. The only commitment I have to Vodafone is for the following month. This has been a painful journey so far (various empty promises and "we're working hard to fix the problem" - I don't think so) and I'm not going to extend it if I don't have to.

Before posting this morning, I did take the precaution of checking that the issue hadn't gone away overnight. It hadn't. but I did note the "Notice of planned service downtime – My Vodafone won't be available from 12am - 6am on Friday 17 August due to planned maintenance" so we may yet be lucky.

I have the same error, on the only account I have, which has been around since 2010. The app does work for me at the level of checking how much data I have left, but it's going to be a bit of a pain next time I want to turn my Extra Data back on, and last time I tried to top up by voucher I had to use the 2345 route because the app interface wouldn't work. (It went all the way to the captcha and then decided there was a problem. But maybe I was typing the number in wrong and it's not connected to the account issue.)

I agree with the person above who said that it can't be efficient to deal with everyone individually for what seems to be a widespread error.

I've had a response from the ticket I raised in the private message as below

"Thanks for contacting us, apologies about the delay in getting back to you. I'm sorry your having issues logging into your online account. I understand the importance of you having access to this and it's something I'd like to help investigate further for you.

In order for me to access your account can you please confirm the 4-digit code I've sent to your mobile number ending 781

Once this has been confirmed I'll get back to you"

I have responded as below

"I'm sorry that feel you need to access my account(s). This issue clearly has little to do with only my account(s) as others have reported that account numbers start with AM have the same issue. I have two accounts with identical problems so I don't know which one you are referring to.

I respectfully ask you to look at your systems and try another test account that starts with AM to reproduce the problem. I think you are likely to find the same error code I encountered on both my systems and the same as others have reported on the community thread."

I won't be going down this route as the error message is clear and any organisation with any development and testing facilities can reproduce this at will.

I've been using Vodafone for some time but this long drawn out poor support simply reinforces my view that Vodafone is not fit to support their customers properly. Online documentation is poor and it seems that the customer is at fault until proven otherwise. This problem has nothing to do with my account and I'd urge others to respond the same way and not get drawn into into password resets and address changes that seem to be the first port of call.